Effectiveness of Severe Acute Respiratory Syndrome Coronavirus 2 Messenger RNA Vaccines for Preventing Coronavirus Disease 2019 Hospitalizations in the United States

Abstract

Background As SARS-CoV-2 vaccination coverage increases in the United States (US), there is a need to understand the real-world effectiveness against severe Covid-19 and among people at increased risk for poor outcomes. Methods In a multicenter case-control analysis of US adults hospitalized March 11-May 5, 2021, we evaluated vaccine effectiveness to prevent Covid-19 hospitalizations by comparing odds of prior vaccination with an mRNA vaccine (Pfizer-BioNTech or Moderna) between cases hospitalized with Covid-19 and hospital-based controls who tested negative for SARS-CoV-2. Results Among 1212 participants, including 593 cases and 619 controls, median age was 58 years, 22.8% were Black, 13.9% were Hispanic, and 21.0% had immunosuppression. SARS-CoV-2 lineage B.1.1.7 (Alpha) was the most common variant (67.9% of viruses with lineage determined). Full vaccination (receipt of two vaccine doses ≥14 days before illness onset) had been received by 8.2% of cases and 36.4% of controls. Overall vaccine effectiveness was 87.1% (95% CI: 80.7 to 91.3%). Vaccine effectiveness was similar for Pfizer-BioNTech and Moderna vaccines, and highest in adults aged 18-49 years (97.4%; 95% CI: 79.3 to 99.7%). Among 45 patients with vaccine-breakthrough Covid hospitalizations, 44 (97.8%) were ≥50 years old and 20 (44.4%) had immunosuppression. Vaccine effectiveness was lower among patients with immunosuppression (62.9%; 95% CI: 20.8 to 82.6%) than without immunosuppression (91.3%; 95% CI: 85.6 to 94.8%). Conclusion During March–May 2021, SARS-CoV-2 mRNA vaccines were highly effective for preventing Covid-19 hospitalizations among US adults. SARS-CoV-2 vaccination was beneficial for patients with immunosuppression, but effectiveness was lower in the immunosuppressed population.

COVID-19-associated hospitalizations among vaccinated and unvaccinated adults ≥18 years – COVID-NET, 13 states, January 1 – July 24, 2021

“…Those aged ≥75 years, LTCF residents, those who are immunocompromised or have multiple underlying conditions may be among the most vulnerable to severe infection and the least likely to mount an adequate immune response to immunization; given early receipt of the vaccine, these populations may also be vulnerable to any potential waning of effectiveness over time. 4,15,16 Increased vulnerability to severe disease resulting in hospitalization, even if fully vaccinated, supports the importance of vaccination among LCTF staff and visitors in protecting persons vulnerable to severe COVID-19. The high proportion of fully vaccinated patients who were immunocompromised also supports the recent recommendation for a third vaccine dose for immunocompromised adults who had previously received mRNA vaccines, although more research is needed to understand the extent to which an additional dose of vaccine results in increased protection in immunocompromised individuals.…”

“…12 Population-based hospitalization rates will be a critical metric in the continued assessment of the effectiveness of vaccines in the population, and complementary to vaccine effectiveness studies using other methods. 4,18 The much higher rates observed in unvaccinated persons compared to vaccinated adults suggest that vaccines remain highly effective in preventing hospitalization for COVID-19 illness. Continuing to increase vaccination coverage in all eligible groups is crucial to preventing severe COVID-19.…”

“…2 Consistent with other studies, data from the Centers for Disease Control and Prevention’s (CDC) Coronavirus Disease 2019-Associated Hospitalization Surveillance Network (COVID-NET) have previously shown that all three vaccine products currently available are highly effective in preventing hospitalization in adults aged ≥65 years. 3,4 Infections in fully vaccinated persons (i.e., vaccine breakthroughs cases) are expected, 5 even in the setting of highly effective vaccines. While most infections occurring in fully vaccinated individuals have been mild or asymptomatic, 5 more serious SARS-CoV-2 infections can occur in fully vaccinated individuals.…”

“…While most infections occurring in fully vaccinated individuals have been mild or asymptomatic, 5 more serious SARS-CoV-2 infections can occur in fully vaccinated individuals. 4 However, the characteristics of fully vaccinated patients hospitalized with COVID-19 and factors associated with risk of vaccine breakthrough have not been well described. Using COVID-NET data representing >67,000 COVID-19-associated hospitalizations from January–June 2021, we compare characteristics of persons hospitalized with laboratory-confirmed SARS-CoV-2 virus infection by vaccination status and assess characteristics of hospitalized cases with vaccination breakthrough.…”

Efficacy of the mRNA-1273 SARS-CoV-2 Vaccine at Completion of Blinded Phase

“…Despite differences in the definitions of disease severity, the vaccine efficacy is supported by real-world data: vaccination has been shown to be highly effective in preventing severe Covid-19, associated hospitalizations, and deaths, as well as mild or asymptomatic infection, regardless of race and age. 9 , 12 , 18-20 …”